Rheostat with rocking contactor



y 1954 H. D. TIMM RHEOSTAT WITH ROCKING CONTACTOR Filed April 8, 1952 Patented May 11, 1954 "RHEOSTAT WITH ROCKING GONTACTOR Harold D. Timm, Milwaukee, Wis., .assignor 11:0 Allis-Chalmers Manufacturing Company, :Mil-

.waukee, Wis.

Application-April-S, 1952;SerialNo. 281;)94

4 Claims. :1

Thi invention relates in general to electrical regulat-ing devices-and inparticular to regulat- :ing devices of the variable resistance type.

'rheostats of the rocking sector type, in which "an arcuate conductive sector is rocked about a pivotpoint alonga path on anarcuate commutator tothe segments of which a plurality of resistance-sections are connected, it isnecessary to suspend the sector relative to the commutator. pension'utilized two springs secured tothe edges of the sector and to a panel or other suitable mounting means. These springsrhad their axes aligned when the sector was in a 'median position. to center the-sector about, a line perpendicular to ,a:line through the axes of the springs. This suspension .is suitable iorrsmaller sectors which donotanove toogreat a distance between themedian position and either of the extreme positions. aHowever, when larger sectors "are utilized, the misalignment of the axes of the springs as the sector departs from. the median positionproduces a substantial moment arm for thesepsprings, especially in the extreme positions of the sector, to produce a torquetending toslip the sector alon the commutator. This slipping action 'resultsin erratic-operation of the device and increased wear on the engaging parts-and is therefore-very undesirable.

This disadvantage maybe overcome by utilizing-suspension means for the sector which producesubstantially-no slipping torque onthe sector regardless of the sector size or position. I One of the-most suitable oi-suchsuspensionmeans comprises springmeans disposed'in a plane parallel to the plane including the pivot pointand the path of sector travel and secured to'the sector at apoint which'rnoves onlyslightly during the sector movement.

Itis therefore an object of this invention'to provide aregulating device of the rocking sector type which is'rugged, reliable and economicalto manufacture.

It'is a furtherobjectof the present invention to provide improved suspension --means for the sector of a-rocking sector type regulating device in'which substantially no undesirable torques act on the sector.

It is an additional'object-of this-invention to provide improved suspension means fora regulating device of the rocking sector type. in which the sector has substantiallyno tendency to slip on its associated commutator.

Objects and 'advantages other than those set .forth :above will be apparent from the following Heretofore, one method'of such-'susdescription when read in connection with'the ac companying drawing, in which:

:Fig. 1 is a view in elevation of-one embodiment of the present invention disposed for mounting with the sector axis horizontal;

Fig. 2 is a cross section view taken in the-plane of line II-II of Fig 1;

Fig. 3 is an'enlarged View ofa portion of the sectional view of Fig; 2

Figs. 4 and 5 diagrammatically illustrate the action of the suspensionmeansof this invention whenthe sector isin both of its extreme Positions; and

Fig. 6 illustrates an alternate embodimenttof the invention disposed for mounting with the sector axis vertical.

Referring more-particularly to the drawing by characters of reierencareference numeral tidesignates a vertical panel which'is preferably made of'metal'and-is designed to support a commutator with'the cooperating brush and'the brush actuating .means. The drawing shows only a portion of panel 6 supporting'a single commutator comprising a plate I of insulating material of suitable shape fastened on panel 6 and covering an apertur -through the panel 6. Plate 'lis made of asuitableinsulating material, such as laminated synthetic resinor impregnated asbestos, and is provided with a plurality of holes to receive a plurality of conductive studs- HJ preferably madeof brass, of which only four are shown in Fig. 2 to retain simplicity inthe drawing.

The studs penetrate through the plate land are "fastened therein by means of nuts H, and are preferably arranged in two adjacent concentric circular rows. The studs carry brackets I2 to support the different sections of a resistor 13 inconductive-contact with the studs to thereby permit a variable number of sections-of the re sistors-tobe connected ina circuit by means of the commutator. Only two. sections of resistors l3 areshownin Fig.2, but it will be understood that ingeneral each segment of one row is connected with the two adjacent segments of the other row through two sections ofthe resistor.

The studs are knurled'on a portion of the length thereof, the projections of the knurled portions engaging with the-walls of the complementary holes of plate l to thereby prevent the studsfrom turning when the nuts thereof are tightened. It will be understood thatthe-commutator maybe constructed in any othersuitableknown. manner which provides the desired rigidity and insulation.

"The extensions of all the studs penetrate through the aperture-of panel 6 and extend beyond the surface of the panel, and are arranged in side by side spaced relation, the extensions I4 and I6 being interleaved to form the segments of the commutator which are machined after assembly of the studs to form a contact path.

The commutator above described is more particularly adapted to engage with the arcuate brush portion 20 of a conductive sector 2| adapted to rock on the commutator along a path defined by a notch or groove 22 provided in the commutator as shown in Fig. 3. Arcuate brush portion 20 is preferably made of graphite and the remaining portion of sector 2| is preferably made of light sheet metal provided with a needle point 23 resting in a jeweled cup 24 mounted on a spindle 25 through a spring 28. The spindle may be caused to oscillate by means of a link 21 connected with any suitable known actuating means (not shown), the spindle then imparting to sector 2| a rocking movement along the con tact path of the commutator. The sector is connected by means of flexible conductor 28 to an insulated terminal 29 on panel 6 to which one terminal of the circuit to be controlled is connected.

Spring 26 urges sector 2| in contact with the commutator and suitable spring means are provided for centering the sector on the commutator. Such spring means are preferably disposed with their axis in the plane 3| including pivot point 23, the center line of arcuate brush portion 23 of sector 2|, and the center line of the contact path. For a horizontal mounting of the device, as shown in Fig. 1, the spring means may comprise a single spring 32 disposed in an opening 33 of sector 2| and secured at one end to an extension or lug 34 of sector 2|. The other end of spring 32 is secured to a stud 35 which is in turn secured to panel 6. Spring 32 preferably has its longitudinal axis substantially parallel to the chord between the ends of arcuate brush portion 20 when the sector is in the median position shown in Fig. 1. Spring 32 carries the weight of the sector and acts to center the sector on the commutator at the median position shown. in Fig. 1.

As the sector rocks about its point or contact 1 with the commutator in a hypocycloid path and departs from its median position, the axis of spring 32 oscillates about the chord between the ends of arcuate brush portion 2|} and gradually departs, but only slightly, from substantial parallelism with the chord between the ends of the commutator. At the extreme position of the sector, shown in Figs. 4, 5, it will be seen that the end of extension 34 to which spring 32 is secured has moved only slightly from its median position. Spring 32 is thus maintained substantially parallel to the chord between the ends of the commutator. The end of extension 34 has only a negligible amount of movement in any direction so that spring 32 retains substantially the same length and tension at all positions of the sector, thereby producing substantially no torque tending to slip the sector on the commutator. The operation of the sector is thus smooth and dependable. Additionally, by disposing spring 32 in the plane 3| between pivot point 23 and the center line of arcuate brush portion 20, no torque is produced which tendsv to pull the sector in a direction perpendicular to the desired direction of sector movement.

It will be seen that if arcuate brush portion 20 of the sector is of sufficient width, the spring means may be disposed adjacent to sector 2| along plane 3| without necessitating the provision of an opening in the sector.

In Fig. 6 is shown an alternate embodiment oi the invention for vertical mounting of the sector. As shown, an additional spring 40 is provided secured to extension 34 and panel 6 and having its axis aligned with the aXis of spring 32 when the sector 2| is in the median position shown. Springs 32, 4!] center sector 2| in its median position and operate in a manner similar to that described above for spring 32 alone to produce a minimum of undesired torque on sector 2| in all positions thereof.

Although but two embodiments have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. An electrical regulating device comprising an arcuate commutator having a plurality of segments, a resistor having a plurality of sections connected to said segments, supporting means for said commutator, a conductive sector having an arcuate portion forming a brush adapted to rock on said commutator, a spring secured to said supporting means and secured tosaid sector for centering said sector at a median position in rocking engagement with said commutator, and means for moving said sector in rocking engagement with said commutator in either direction from said median position, said spring having its axis disposed substantially parallel to the chord between the ends of said commutator when said sector is in said median position, said spring being secured to said sector at a single point substantially on the center line of said brush for maintaining said axis substantially parallel to said chord in any other position of said sector to prevent said spring from slipping said sector along said commutator.

2. An electrical regulating device comprising an arcuate commutator having a plurality of segments, a resistor having a plurality of sections connected to said segments, supporting means for said commutator, a conductive sector having an arcuate portion forming a brush adapted to rock on said commutator, a spring secured to said supporting means and secured to said sector for centering said sector at a median position in rocking engagement with said commutator, means for moving said sector in rocking engagement with said commutator in either direction from said median position, said spring having its axis disposed substantially along the chord between the ends of said commutator when said sector is in said median position, said spring being secured to said sector at a single point substantially on the center line of said brush for maintaining said axis substantially along said chord in any other position of said sector to prevent said spring from slipping said sector along said commutator.

3. An electrical regulating device comprising an arcuate commutator having a plurality of segments, a resistor having a plurality of sections connected to said segments, supporting means for said commutator, a conductive sector having an arcuate portion forming a brush adapted to rock on said commutator, spring means secured to said supporting means and secured to said sector for centering said sector at a median position in rockmg engagement with said commutator, and means for moving said sector in rocking engagement with said commutator in either direction from said median position, said spring means being disposed to exert its force on said sector in a direction parallel to the chord between the ends of said commutator when said sector is in said median position, said spring means being secured to said sector at a single point substantially on the center line of said brush to exert its force on said sector in a direction substantially parallel to said chord in any other position of said sector for preventing said spring means from slipping said sector along said commutator.

4. An electrical regulating device comprising an arcuate commutator having a plurality of segmerits, a resistor having a plurality of sections connected to said segments, supporting means for said commutator, a conductive sector having an arcuate portion forming a brush adapted to rock on said commutator, spring means secured to said supporting means and secured to said sector for centering said sector at a median position in rocking engagement with said commutator, and means for moving said sector in rocking engage ment with said commutator in either direction from said median position, said spring means being disposed to exert its force on said sector along the chord between the ends of said commutator when said sector is in said median position, said spring means being secured to said tor at a single point substantially on the center line of said brush to exert its force on said sector substantially along said chord in any other position of said sector for preventing said spring means from slipping said sector along commutator.

References Cited in the file of this patent UNITED STATES PATENTS Number 

